The present invention relates to a device for closing molds of an injection molding machine for plastic and, more particularly, to such a mold closing device having a stationary end plate that is connected to a mold clamping plate which is moveable on traverses via a toggle lever mechanism having a double toggle lever.
During injection molding of plastic, mold halves are moved towards and away from each other during pauses in the cycle between casting and ejection of the cast article. For this purpose, a moveable mold clamping plate is displaced on traverses. This moveable clamping plate can be actuated directly by drive units or by a toggle mechanism.
An exclusively hydraulic embodiment has the disadvantage that, as a whole, one or more piston-cylinder units designed for relatively high pressures are necessary. In addition, the hydraulic pressure in this completely hydraulic machine must be retained when the machine is locked.
From EP-PS 01 64 419, a closing device for closing molds of an injection molding system is known in which a link mechanism is moveable by a spindle nut that is driven by a servo motor. Such embodiment has the disadvantage that the drive motor as well as the spindle nut protrude considerably in all embodiments described in the patent. The interference with the space between end plate and moveable clamping plate specifically upon a non-concentric arrangement is also disadvantageous.
From Federal Republic of Germany Patent 29 09 738 a form-locking device for injection molding machines for injection-compression molding of plastic parts is known in which a centrally arranged cylinder of a piston-cylinder unit has a stop at its end, the stop being adjustable in accordance with a compression stroke. The injection molding machine of the mentioned patent takes up a large amount of space due to the cylinder which extends out of the machine plus the adjusting device. By the central arrangement of the piston-cylinder unit, furthermore, the space between the end plate and the moveable mold clamping plate in the center is filled up.